The following correction was printed in the Guardian's Corrections and clarifications column, Saturday November 4 2006

Aspirin does not increase the risk of heart disease and stroke, as we said in the article both above and below. On the contrary, research shows that aspirin can reduce this risk, and it is taken by many people for that reason. The Commission on Human Medicines, which warned that some non-steroidal anti-inflammatory drugs may be associated with a small risk of heart attack or stroke, did not include aspirin in the warning.

The latest news that common painkillers raise the risk of stroke or heart attack could come as a blow to Britain's many pill poppers. The Commission on Human Medicines (CHM) last week wrote to every doctor in the UK warning them that non-steroidal anti-inflammatory drugs (NSAIDs) - a family of painkillers that includes household favourites such as ibuprofen and aspirin - "may be associated with a small risk of ... heart attack or stroke" if used for a long time. It seems that our medicine cabinet staples, not to mention some pills prescribed by the trusty GP, may not be so benign after all.

For millions of arthritis, migraine and back-pain sufferers, along with quite a few pill-snaffling hypochondriacs, this is potentially unsettling news. Research shows that for every 1,000 people taking NSAIDs, three a year will suffer a related heart attack. When all heart attacks, stroke or vascular disease are taken together, the risks increase by 40%. These days we see painkillers as a normal part of everyday life. Even people who do not suffer chronic pain carry around packets of Neurofen "just in case", and many of us will down a couple of aspirin purely to ward off a potential headache. Some parents of small children can be particularly cavalier, erroneously spooning Calpol - infant paracetamol - into their offspring simply to "prevent" night-time waking.

At the other end of the spectrum, meanwhile, lie the stoics. "I often see people with appalling toothache, but they have taken nothing for it," says Laurie Powell, a dentist from Bicester. "They are suffering awful pain totally unnecessarily, through fear or suspicion."

"People can be unnecessarily scared about taking painkillers," agrees Jane Quinlan, consultant anaesthetist and acute pain specialist at the John Radcliffe Hospital Trust, Oxford. "People have huge misconceptions about supposed dangers. I see a lot of patients who have major surgery and are reluctant to take their painkillers because they think they will become addicted. In fact, the percentage of people becoming addicted to painkillers after major surgery is minuscule."

Analgesia has never been so accessible. Not long ago, painkillers were unpalatable horse-pills kept in glass bottles for rare use and only available from the pharmacist. It is easy to forget that it was only in 1996 that corner shops and supermarkets started selling them.

The three main over-the-counter painkillers are aspirin, paracetamol and ibuprofen. Aspirin and ibuprofen are NSAIDs. They reduce pain, fever and inflammation, while paracetamol, which is not a NSAID, reduces only pain and fever and not inflammation. These drugs - along with weak opioids such as codeine - are excellent at relieving all kinds of pain, including arthritis, muscle and ligament pains (strains and sprains), period pain, post-operative pain, headaches and migraines.

NSAIDs work on chemicals in your body called prostaglandins which are involved in inflammation, and also sensitise nerve endings, causing pain. The drugs stop your body from making as many prostaglandins, so you have less inflammation and therefore less pain. It is still not clear exactly how paracetamol works but doctors believe that it lowers temperatures and dulls pain by blocking prostaglandins in the brain.

NSAIDs are clever drugs, and have benefits beyond pain management. Many older people take a low-dose aspirin every day because studies show that it can thin the blood, reducing the risk of clots that can lead to a heart attack or a stroke. Research has also shown that ibuprofen and aspirin may offer some protection against breast cancer, and cancers of the mouth, colon, throat and oesophagus. "There is scientific evidence to suggest that aspirin and other anti-inflammatory drugs can help to prevent some types of cancers from developing," says Anthea Martin, science information officer at Cancer Research UK. However, "People should not start taking aspirin in order to reduce their chances of getting cancer unless advised to by their doctor". The side-effects outweigh the possible benefits.

All painkillers, in fact, have side-effects. Paracetamol is the first rung on the GP's so-called "Analgesic Ladder" because it has the fewest. But an overdose of just 15g - that is about 30 tablets - can cause fatal liver damage. In fact, deliberate paracetamol overdose is one of the most common causes of liver transplants in Britain.

NSAIDs, meanwhile, if used over several months, can not only raise your risk of a coronary but can attack your stomach lining, causing stomach ulcers or bleeding. This risk increases the longer you take the drugs: doing so for days is usually safer than for weeks or months. There are other downsides: NSAIDs can trigger an asthma attack in about 10% of asthma sufferers, can cause renal failure, may interact badly with other medications, and can damage an unborn child (paracetamol, on the other hand, is safe to take when pregnant or breastfeeding). These drugs may be effective, but they are hardly risk free.

One of the stronger painkillers is codeine, an "opioid" drug related to morphine. You can buy codeine-based products in pharmacies (Nurofen Plus contains codeine, as does Solpadeine and Feminax for period pains), or your doctor may prescribe them. Codeine is very effective but it, too, has downsides: it can make you sick, drowsy or constipated, itchy, sweaty or dry mouthed, and very occasionally, may make you hallucinate.

On the plus side, codeine can make you delightfully relaxed and serene. This is why prescription painkillers such as Vicodin in the US - known as "Vikes" - have become infamous in recent years as the addiction of choice for stressed-out celebs, who can always blame back pain when they enter rehab. It is also why the mothers of small children have been known to pop a couple of calming Feminax at tea time as "mother's little helper", the mild and modern answer to Valium.

"It is not uncommon for us to see codeine addiction," says GP Louise Hoult. "People take it for a variety of conditions and certain people can become addicted." Dr Quinlan agrees: "If you do find yourself taking the drug purely because it makes you happy this could be an addiction." However, she says: "If you follow the dosage on the bottle and do not self-medicate for more than a day or two without your GP's advice, addiction to codeine is extremely unlikely."

There is, then, no need to sweep the contents of your bathroom cabinet into the bin or suffer with a stiff upper lip, even if you have long-term pain. The European Medicines Agency has ruled that NSAIDs are more beneficial than harmful if you do not have cardiovascular or gastrointestinal problems. "It is perfectly reasonable to take NSAIDs for long-term pain, as long as you do so with your doctor's advice," says Dr Quinlan. "It is about striking a risk-benefit balance."

So, talk to your GP about pain relief if you need it for more than a couple of days. If long-term pain is ruining your life, some calculated risks may be worth taking.

Pills at a glance

Paracetamol

Good for: mild to moderate pain - headaches muscle and joint pain, backache, period pains. Can bring down a high temperature. No good for: inflammation. Side-effects: minimal, but liver damage can occur with overdose.

Talk to your doctor if: you have poor liver function or are an alcoholic (both paracetamol and alcohol can harm the liver).

NSAIDS (such as ibuprofen and aspirin)

Good for: reducing fever and pain and inflammation from arthritis, rheumatism, back pain, sports injuries and other mild to moderate pains. Possible side-effects: stomach ulcers, asthma attack, renal failure. May interact badly with other medications. Talk to your doctor if: you have stomach or gastrointestinal problems, have previously had a heart attack or stroke, are pregnant, or need to take them over several months.

Opoids (such as codeine)

Good for: moderate to severe pain, ie backpain, migraine. Possible side-effects: nausea, vomiting, drowsiness, constipation, dry mouth, itching, sweating and hallucinations. Talk to your doctor if: you have asthma, liver or kidney disease, are an alcoholic, pregnant, need to self-medicate for more than a day or two, or think you are taking them because you like the feeling.

Keys, wallet, phone, pain killers
'I swallowed about 10 a day'

Perhaps half a decade ago, I began to think I might be taking too many painkillers. There were the ones I took first thing in the morning, ideally a trio of NurofenPlus, or four ordinary Nurofen, washed down with a gargled mouthful of tap water. This was to deal with the hangover I hadn't quite knocked out with the pills I'd taken the night before. In any case, I carried on popping ibuprofen through the day, right up until the moment I set out for the pub in the evening, when I was beginning to feel better.

One day, I found myself in someone's house with a bit of a headache. No problem, he said - he'd stocked up on painkillers. He thought he had four packets of 12. But he couldn't find them. The packets had all gone. Three people were living in the house. "I just bought them a couple of days ago," he said. That's when I decided to look into the business of painkillers a bit more closely.

It occurred to me that it couldn't be just me - our whole relationship with painkillers had changed drastically in my lifetime. When I was growing up, pills were kept in a glass bottle in the medicine cabinet in the bathroom. When you had a headache, you would wait until you got home and then open the dusty bottle and shake out two pills - they were round, powdery discs. They were difficult to get down. They had a "bisect line" - a groove cut into the pill so you could snap it in half if you wanted a reduced dose.

And now look - these days, painkillers are things you carry on your person; if you feel a headache coming on, you pat your pockets. When people leave the house, they might do a last-minute check: keys, wallet, phone, painkillers. The point is that the time between pain and treatment has shrunk to almost nothing. These days we don't have time to waste on pain. Never mind the fact that pain is a natural process, and sometimes a useful one.

I was right about it not being just me. As a market sector, painkillers were booming, particularly ibuprofen, which has been available in supermarkets and corner shops since 1996. These days, they don't come in bottles, but in bright, shiny packets, some of which are shaped like mobile phones; they are elegant enough to put on a table at a restaurant. And their smooth edges make them easy to swallow. Some have a glossy coating of hard sugar, like Smarties or M&Ms. Some of them are mint- or lemon-flavoured. Some come in capsule form, and look like vitamin pills. According to Euromonitor International, in 2000 the analgesics market was worth £461.5m. By 2010 they predict that it will reach £574m.

At my height, I swallowed around 10 pills a day. Was I damaging my health? Probably. One doctor I met believed that a regular intake of analgesics can actually make headaches worse - if you dull your pain pathways, they end up getting more sensitive. Pain is our bodies' way of telling us something. Maybe we should listen.
William Leith

· William Leith is the author of The Hungry Years (Bloomsbury £7.99), a memoir of bingeing